They've been described as the "gods of the court" — the report writers whose written assessments can affect the Family Court's decision on which parent gets custody of their children.

Key points:

Practitioner who performs expert witness work in family court under inquiry

Parents lodged series of complaints with health regulators

Family Court says private report writers "not compelled to comply" with its standards

For parents who say the report writer got it wrong, the choice is stark: pursue the legal "fight of your life" to overturn the report or accept losing custody of your kids.

Family report writers are usually social workers, psychologists or psychiatrists.

Now, a group of parents has banded together to launch a challenge against one report writer in New South Wales, alleging his practices "place the public at risk".

The group has accused him of a string of failures including "grossly inaccurate and incomplete" recording of interviews, "misdiagnosis", and that he "applies unscientific theory", particularly in response to allegations of child abuse and family violence.

Their campaign has resulted in the alleged problem practitioner being referred to the Medical Council of New South Wales, a body that has the ability to suspend the practitioner's registration if it believes the public is at an immediate risk.

One member of the group has told the ABC the work of the report writer had caused "irreversible damage" to their family.

"Our lives are certainly never going to be the same again and I feel open disgust for a system that tolerates somebody who is so obviously acting outside the law and outside his expertise," Kellie* said.

"If a report is wrong and the court relies on it, it destroys lives, particularly the children's."

The group of parents hope their action will bring renewed scrutiny to the regulation of Family Court report writers, who critics say can operate "beyond the rule of law".

"We certainly see it as a milestone shift in the regulator's position because they've held the wrong position for years that these [practitioners] engaged by the court are beyond the reach of regulation and in a sense, beyond the rule of law," Kellie said.

One Sydney-based psychologist with more than 30 years' experience told the ABC he saw the work of the alleged problem practitioner after several parents came to him seeking a second opinion.

The psychologist, who did not want to be named, said on several occasions he prepared secondary reports that were submitted to court.

"The work I've seen has had dramatic effects upon the parents involved and I reached different conclusions, very different conclusions," he said.

"It's questionable that someone should diagnose a personality disorder based on a few interviews only, particularly in an acrimonious situation.

"The difficulty is judicial or legal decisions are made on that where people may lose custody of their children when there may be very little basis for that."

In family law matters, report writers meet with families, make an assessment of issues within the case and prepare a report of recommendations for judges to consider when deciding the best arrangement for children involved in custody battles.

Concerns about these practitioners go beyond one case and extend to the lack of governance over the entire process of report writing.

In an overburdened court system, barristers and lawyers have told the ABC the recommendations in expert reports can be heavily considered in deliberations.

One parent advocate told the ABC challenging a family report, or "counteracting the gods of the court", would be "the fight of your life".

Similar comments were made in submissions to last year's parliamentary inquiry into Australia's family law system.

In December, that inquiry handed down its report and recommended "abolishing private family consultants" as well as establishing a "national accreditation system" that included a "complaints mechanism for parties when family consultants do not meet the required professional standards".

Private report writers 'not compelled to comply' with standards

The practitioner at the centre of the recent complaints is a private family report writer, or, a single expert witness. Currently, there is no accreditation for conducting this kind of work.

Family report writers do not need to have clinical experience, and while specialised training in dealing with violence and abuse allegations is encouraged in a set of guidelines, it is not compulsory.

The Family Court of Australia said an accreditation system for internal family consultants "would be unnecessary" as that work is already the responsibility of the courts.

In a submission to the current Australian Law Reform Review, Family Court Chief Justice John Pascoe said:

"An accreditation scheme which allows parties to ascertain that a private report writer has acquired and maintained the required competencies and works to a high standard could greatly assist both litigants and the court to which the report would be submitted."

"Largely a regulatory regime would be for government, but equally there is a massive ability through the rules of court to ensure there are certain standards that have to be met by experts and that is a process which has to be designed in the court," he said.

Australia's federal courts:

High Court of Australia

Federal Court of Australia

Supreme Court

Family Court of Australia

Federal Circuit Court of Australia

Family law matters are dealt with in the Family Court and the Federal Circuit Court (FCC) as well as the Family Court of Western Australia.

"At the moment you've got two different courts with two different sets of rules dealing with essentially the same matters which has proven to be a great failure."

Mr Porter said the planned amalgamation of the Family Court of Australia and the Federal Circuit Court would help, "ensure that costs of experts of a variety of types are kept to a minimum".

In some judgements, parents are ordered to pay several thousand dollars each for a single report.

In some cases, judges name the private family report writer parents who must engage in interim court orders, but there is no regulation for what that practitioner can charge.

Federal Liberal MP Craig Kelly has campaigned for regulation of these practitioners, particularly their fee structure.

"They should be given a list of people they can go to to get this done," Mr Kelly said.

"To allocate it to one person where one person is given basically a monopoly position where they can charge whatever they want is against every principle of justice, of fairness and equity and every economic principle we abide by," he said.

Parents turn to health regulators

The Family Court and the Federal Circuit Court have a complaints process for report writers employed internally.

After hitting dead ends with the courts when trying to complain about private practitioners, both Kellie* and another advocate who spoke to the ABC had some success complaining to the relevant health authorities.

In NSW, the Health Care Complaints Commission (HCCC), the Medical Council, and the national health regulator, the Australian Health Practitioner Regulation Agency (AHPRA), govern registered health practitioners together under what's referred to as a co-regulatory arrangement.

In this case, the HCCC received the parents' complaints and decided to refer them to the Medical Council.

In one response to the group, the HCCC said there were, "concerns about the conduct" of the practitioner, "in relation to his use of particular clinical theories and his interview techniques" and that it was a, "broader issue of conduct outside of a specific family law case".

The HCCC confirmed to the ABC it had received "a number of different types of complaints" about the practitioner.

The Medical Council does not have the power to investigate the claims, but can conduct inquiries and suspend a practitioner if there is an immediate risk to the public.

If it decides a full investigation is required, the complaints will be batted back to the HCCC and the public may be consulted.

The Medical Council told the ABC national law, "makes it an offence to disclose information about complaints" it receives, but each would be, "considered according to its facts".

In May last year, the Federal Government directed the Australian Law Reform Commission to conduct a "comprehensive review" into the family law system. That inquiry is due to deliver its report to the Attorney-General in March 2019.

Mr Porter said if that inquiry returned recommendations about regulation of family report writers, the Government would take them "very seriously".

'The public doesn't know how bad this is'

A former president of the Clinical Psychologists Association of Australia and a psychology clinic director at the University of Sydney, Judy Hyde, said the level of training family report writers were required to have was "scary".

"The public doesn't know how bad this is," she said.

The players:

Judges/Magistrates

Barristers

Counsels

Independent Children's Lawyers

Litigants (usually parents)

Children

Expert witnesses, particularly family report writers

"This is terrible because what they're saying is, we're prepared to have people with unaccredited training undertake assessments of very complex, specialised, difficult cases where people's lives are based on the decisions that are made for them.

"For the rest of their lives it will have an impact."

Ms Hyde made the point that other types of assessments have registers of approved suppliers.

"WorkCover requires you to have accredited training for WorkCover … that should be the same at least for the children that we're trying to deal with and help manage their lives going forward," she said.

Ms Hyde acknowledged family law was a difficult area of practice for assessors.

"There are complaints made by people who haven't got what they wanted, but the fact is people are very poorly trained to actually manage these assessments anyway and the lives of our children are put at risk," she said.